1. Field of the Invention
The present invention relates to a liquid crystal display apparatus.
2. Description of the Related Art
The liquid crystal display apparatus is widely utilized as a display apparatus for a computer, a car navigator system, a television set and the like. A liquid crystal display apparatus generally includes a liquid crystal display panel having a plurality of matrix arrays of liquid crystal of pixels, a backlight for illuminating the liquid crystal display panel, and a display control circuit for controlling the backlight and these display panels. The liquid crystal display panel has a liquid crystal layer held between an array substrate and a counter-substrate.
The array substrate includes a plurality of pixel electrodes disposed in substantially a matrix form, a plurality of gate lines disposed along a plurality of lines of pixel electrodes, a plurality of source lines disposed along a plurality of rows of pixel electrodes, and a plurality of switching elements disposed near intersections of the plurality of gate lines and the plurality of source lines. Each switching element includes a thin film transistor (TFT), and when one gate line is driven, the switching element conducts and applies potential of one source line to one pixel electrode. The counter-substrate is provided with a common electrode such that it is opposed to the plurality of pixel electrodes disposed on the array substrate. One pixel electrodes and the common electrode constitute a pixel together with a pixel region which is a portion of a liquid crystal located between these electrodes, and controls liquid crystal molecule array in the pixel region by an electric field between the pixel electrode and the common electrode. The display control circuit includes a gate driver which drives the plurality of gate lines, a source driver which drives the plurality of source lines, and a controller circuit which controls the gate driver, the source driver and the backlight.
When the liquid crystal display apparatus is for a television set which mainly shows a moving image, a liquid crystal display panel of an OCB (Optically Compensated Bend) mode in which liquid crystal molecules show excellent response is used.
In the liquid crystal display panel, alignment becomes splay alignment which is almost lying before power is supplied by an alignment film which liquid crystals are rubbed in parallel to each other on the pixel electrodes and the common electrode. The liquid crystal display panel transitions these liquid crystals from the splay alignment to the bend alignment and displays information by relatively strong electric fields which are applied in initializing processing upon supply of power.
The reason why the liquid crystals become splay alignment before power is supplied is that the splay alignment is more stable than the bend alignment in terms of energy in a voltage-non-applied state of liquid crystal driving voltage. A liquid crystal has a property that even if the liquid crystal once transitions to the bend alignment, it reversely transitions to the splay alignment again when a voltage-applied state which is equal to or lower than a level in which the splay alignment energy and the bend alignment energy are competition with each other or a voltage-non-applied state is continued for a long term. Since the splay alignment has quite different characteristics from those of the bend alignment, abnormal display occurs.
Conventionally, to prevent the bend alignment from being reversely transitioned to the splay alignment, there is employed a driving system in which a large voltage is applied to a liquid crystal in a portion of a frame period during which one frame image is displayed. In a normally white liquid crystal display panel, this voltage corresponds to a pixel voltage of black display, and this system is called black insertion driving (Jpn. Pat. Appln. KOKAI Publication No. 2002-202491).
When the liquid crystal display apparatus is used under a low temperature environment, since viscosity of the liquid crystal is increased, the response of the liquid crystal is deteriorated, and a liquid crystal voltage does not reach a target value within predetermined time. This phenomenon is also generated both when a high voltage is applied to carry out black display and when a low voltage is applied to carry out white display. Therefore, if these states are compared with a display state at the room temperature, brightness is lowered in the white display and the screen does not become black sufficiently in the black display.